In modern communication systems, data may be processed at a transmitting device, modulated, filtered, amplified, and transmitted to one or more receiving devices. The transmitted signal typically experiences path loss, multipath interference, and other types of signal degradation before reaching the receiving devices. A receiving device receives the modulated signal, performs various types of conditioning, and demodulates the conditioned signal to recover the transmitted data.
In demodulating the received signal, receiving devices often employ a carrier-recovery loop to remove frequency and phase variations that may exist between the transmitting device oscillator and receiving device oscillator. The carrier-recovery loop typically incorporates a phase-locked loop (PLL) to track and remove the frequency and phase variations. Generally, the loop bandwidths of the PLLs are optimized for peak performance. Such optimization may define operations based on an assumed signal-to-noise ratio (SNR) and/or phase noise power spectral density (PSD).
However, in addition to the signal degradations that occur along the channel, certain receiver components may also contribute to frequency and phase variations. As such, the actual phase noise PSD may well be different from the assumed phase noise PSD—just as the actual operating SNR may be different from the assumed SNR. Such variances may not be stationary and may, therefore, compromise carrier recovery performance.